1. Field of the Invention
The present invention relates to a fuel cell formed by stacking a membrane electrode assembly and separators in a horizontal direction. The membrane electrode assembly includes a pair of electrodes and an electrolyte membrane interposed between the electrodes. A reactant gas flow field is provided for allowing a reactant gas to flow along an electrode surface in the horizontal direction.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (MEA) which includes an anode, a cathode, and a solid polymer electrolyte membrane (electrolyte) interposed between the anode and the cathode. The solid polymer electrolyte membrane is a polymer ion exchange membrane. The membrane electrode assembly is sandwiched between a pair of separators. Normally, a plurality of fuel cells are stacked together, and used in stationary applications. Further, the fuel cells are mounted in a fuel cell vehicle, and used as an in-vehicle fuel cell system.
In the fuel cell, metal separators each having a corrugated shape formed by press forming is used. A fuel gas flow field (hereinafter also referred to as the reactant gas flow field) for supplying a fuel gas to the anode and an oxygen-containing gas flow field (hereinafter also referred to as the reactant gas flow field) for supplying an oxygen-containing gas to the cathode are provided in surfaces of the metal separators. For each of power generation cells, or for every predetermined number of power generation cells, a coolant flow field is provided for supplying a coolant along surfaces of the metal separators.
In this regard, the coolant flow field has structure where a back surface of the fuel gas flow field and a back surface of the oxygen-containing gas flow field are stacked with each other. Thus, the fuel gas flow field and the oxygen-containing gas flow field are corrugated flow fields, and the coolant flow field is formed by stacking the back surfaces of the corrugated flow field in different phases (Japanese Laid-Open Patent Publication No. 2008-293694).